Flexible conveyor apparatus

ABSTRACT

Apparatus includes conveyor belt which is flexible laterally in its own plane for curved paths and carrier framework which is equally flexible for adjustment to any desired plan. Framework has plurality of longitudinally spaced main frames connected by lazy tong linkages at sides to expand and contract longitudinally. Spring force units between successive frames expand apparatus to tension belt. Swinging portions laterally curves the path by contracting inner side of framework while force units keep outer side extended to stretch and tension belt. Sectional track for belt is carried by frames and by lazy tong links.

Unite States Patent [72] Inventors Billy J. Dahlem Golden; John A.Martin, Denver, both 01, C010. [21] Appl. No. 781,718 [22] Filed Dec. 6,1968 [45] Patented June 15, 1971 [73] Assignee Power-Curve ConveyorCompany Denver, C010.

[54] FLEXIBLE CONVEYOR APPARATUS 16 Claims, 12 Drawing Figs.

[52] US. Cl. 198/109, 198/139 [51] Int. Cl ..B65g 15/50, 865g 41/00 [50]Field of Search 198/109, 139,195, 181, 189

[56] References Cited UNITED STATES PATENTS 2,269,078 l/1942 Cartlidgel98/109X 2,576,217 11/1951 Eggleston 198/139 2,678,125 5/1954 Bonney,.1r198/139 2,863,553 12/1958 Nordquist 198/139 3,333,678 8/1967 Rodman198/195 3,416,645 12/1968 Jones..... 198/195 3,450,250 6/1969 Frisk198/189 FOREIGN PATENTS 566,323 1932 Germany 198/127X 797,798 1958 GreatBritain 198/195 Primary Examiner- Edward A. Sroka Attorney- Sheridan andRoss PATENTEU JUN! 5 mm SHEET 3 OF 4 FIG. 7

INVENTURS illy J. Duh/em John A. Marfin /M1 M, f3,

ATTORNEYS FLEXIBLE CONVEYOR APPARATUS BACKGROUND OF THE INVENTION Thisinvention lies in the field of conveyor apparatus of the type whichincludes an endless loop flexible belt which travels along a supportingframe to carry a load between selected stations. Such belts may bemerely idlers driven by the weight of the load on a down slope or theymay be driven to positively transport the load. The invention isdirected more particularly to apparatus of the type mentioned in whichthe conveyor belt is articulated in such fashion that it has asubstantial range of longitudinal expansion and contraction, and eachside edge a may expand or contract independently of the other. Withproper support and guide means such a belt can follow a path which hasstraight or curved portions or both in plan view, the radius ofcurvature of course being limited by the amount of play in thearticulated linkage.

Such belts are in rather general use and carry out their primary purposevery satisfactorily. However, at the present time their utility islimited by the fact that the supporting structures are made up of fixed,rigid frameworks having some predetermined planfonn. Even though a beltis capable of following many varied paths it is provided with only asingle one in a structure which has been designed and built for aspecific installation. If it is necessary to change any part of the pathfor any reason, at least a part of the supporting structure must be torndown and rebuilt. Likewise, a minor miscalculation in laying out theplanform originally may cause interference with other equipment andrequire rebuilding even before initial use.

SUMMARY OF THE INVENTION The present invention overcomes thedifficulties mentioned above and provides a total conveyor apparatuswhich is built of comparatively few different standard parts and may bereadily constructed of any desired width, height and length. In any sizeit is universal in utility and may be permanently installed, modified,or moved to a different location with a minimum of time and effort.

Generally stated, the apparatus employs a generally available endlessloop laterally flexible conveyor belt of any desired length. Any suchbelt, because of the articulation mentioned above, has a maximum lengthand a minimum length. Its minimum radius of curvature in a horizontalplane is a function of the width of the belt, the fully contractedlength of the belt on the inside of the curve, and the fully expandedlength of the belt on the outside of the curve.

The carrier support of the present apparatus is an articulated frameworkwhich is capable of expansion and contraction to a somewhat greaterextent than that of the belt and is capable of being curved laterally ineither direction to at least as great an extent as the belt. In itspresently preferred embodiment it is made up of one or preferablyseveral repeated sections which are about 3 feet long, the most commonone at present comprising six sections and having an overall length ofabout 20 feet.

A typical section is generally rectangular in planform and comprises anopen framework having a vertical main frame member at each corner. Eachpair of laterally opposed frame member is connected by upper and lowercrossmembers rigidly connected to form an open box member symmetricallydisposed about a longitudinal axis of the framework. Vertical standardsextend downwardly from each frame member to support the structure at adesired level, and castered wheels are provided at the lower ends of thestandards to provide mobility for placement or rearrangement.

In order to obtain the desired expansion and contraction, the two mainframe members at either side of a section are connected by alongitudinally extending lazy tong or parallelogram linkage having itsplane generally vertical. The free ends of the linkage are attached tothe respective frame member to provide a general rectangle in planform,the upper free link ends being pivotally connected close to the upperends of the frame members and the lower free link ends being pivotallyconnected somewhat above the bottom ends of the frame members. The pivotpins of these latter link ends, of course, ride in vertical slots in theframe members to allow the necessary expansion and contraction of thelinkage in well-known manner.

It is necessary to provide track means for longitudinal sliding of thebelt. Since the framework must expand and contract longitudinally, thetrack is made up of discrete track portions. In addition to thecrossmembers connecting the main frame members, there are also aplurality of lighter crossbars, one extending between the upper apexpivotal connection of eacli set of the lazy tong links and the laterallyopposite similar connection. A track portion is mounted at each side ofthe framework, on each of these crossbars as well as on the crossmembersconnecting the main frame members, all of which lie in a commonhorizontal plane. It will 'be obvious that as the linkage expands andcontracts, all of the track portions will maintain a variable butcomparatively uniform spacing for best support of the sliding belt.

Whether the particular framework comprises one section or a dozen ormore, the basic standard structural unit is as described above, repeatedas many times as necessary to achieve the desired result. Rotary meansis normally provided at each end of the framework in the form of a drumrotatable about a horizontal axis normal to the longitudinal axis of theframework to support and guide the belt into a return path. In mostcases, at least one drum is power driven to produce the longitudinalmovement of the belt.

Almost all installations are long enough to make it desirable ornecessary to provide a supporting track for the return portion of thebelt to eliminate excessive sag. Where the path has any horizontalcurvature a support and guide track is essential. In the presentconstruction, crossbars similar to the upper crossbars described aboveare connected to the lower apex pivotal connections of each set of thelazy tong links and also to the lower pivotal connection of one end linkof each linkage to its respective main frame member. Track portions aremounted on these crossbars the same as the upper ones to make avariable-length track means.

With the construction described above, it is apparent that the frameworkmay be longitudinally expanded and contracted through a substantialrange, and also that one side may be contracted while the other remainsexpanded, within determinable limits, to cause the framework and trackmeans to form a lateral curve in a horizontal plane. This is facilitatedby providing a suitable amount of play in the various pivotalconnections so that the curve" is made up of a series of short straightlines. The combination of this framework with the laterally flexiblebelt first mentioned provides a conveyor apparatus which may be set upin a straight: line or curved at any portion to avoid obstacles or tolead to any desired point, and which may readily be moved from place: toplace and shaped to meet new requirements. I

The flexible belt must always be fully expanded at the outside of acurve in order to function properly and hence it must be tensioned toeliminate slack. This is accomplished by the use of spring means whichwill yieldingly expand the framework longitudinally to apply a desireddegree of tension in the belt and yet which will yield to the :forces ofcontraction when the combination is curved laterally. In the presentapparatus each section is treated individually by connecting twoelongate force units along the longitudinal centerline and between theupper crossmembers and the lower crossmembers of successive box frames.The units are telescoping rods and tubes with coil springs to expandthem. Thus the entire framework is longitudinally yieldably expanded toapply spring tension to the belt. When one side: of the frameworkiscontracted to form a curve, one or more of the sets of spring units willbe slightly contracted while the side of the framework at the outside ofthe curve remains fully yieldably expanded.

' BRIEF DESCRIPTION OF THE DRAWINGS Various other advantages andfeatures of novelty will become apparent as the description proceeds inconjunction with the accompanying drawings, in which:

FIG. 1 is a side elevational view of a conveyor apparatus embodyingfeatures of the invention;

FIG. 2 is a plan view of a portion of the device of FIG. I to anenlarged scale showing the apparatus formed to a lateral curve;

FIG. 3 is a side elevational view of a section of the framework showingdetails of various articulated parts;

, FIG. 4 is a diagrammatic view in perspective of a section of theframework;

FIG. 5 is an elevational view, relation of various parts;

FIG. 6 is a sectional view taken on line 6-6 of FIG. 3;

FIG. 7 is a sectional view taken on line 7-7 of FIG. 3;

FIG. 8 is a sectional view showing the connection of a force unit to apair of crossmembers;

FIG. 9 is a perspective view of one of the track portions;

FIG. 10 is a perspective view of a portion of the side edge of a typicallaterally flexible conveyor belt;

FIG. 11 is a sectional view taken on line 11-11 of FIG. 10; and

FIG. 12 is a perspective view of a portion of the side edge of aconveyor belt provided with a modified form of track-engaging show.

DESCRIPTION OF PREFERRED EMBODIMENT The total apparatus is generallyillustrated in FIGS. 1 and 2, where it will be seen that in itspreferred form the framework is made up of a plurality of sections 10which are substantially identical in construction and connected inseries to make a carrier support of any desired length. Transferapparatus 12 and 14 is provided at the ends and normally includesrollers 16 and 18. In most cases a roller 16 is driven by a motor 20 topositively move a conveyor belt along the length of the apparatus.

EAch section includes a generally rectangular box member at each endhaving upright main frame members 22 at each side connected by upper andlower crossmembers and supported by standards 24. The frame members oneither side are connected by lazy-tong-type parallelogram linkages 26,the linkage on each side being capable of longitudinal expansion andcontraction independently of the linkage on the opposite side. With thisconstruction the contraction of one side will produce lateral curvatureof the unit or section. When there are a series of sections, as is theusual case, the assembly may be readily adjusted to the planform shownin FIG. 2, where one portion of the length is straight and anotherportion is curved. The conveyor apparatus in general is completed by aflexible belt 28, described in more detail later, which is capable ofassuming the same lateral curvature as the framework.

The details and relation of the principal parts of a section are bestillustrated in FIGS. 3 and 4, where it will be seen that a generallyrectangular box member 30 at each end comprises an upright frame member22 at each side of the framework connected at their upper and lower endsby two crossmembers 32, all being rigidly connected together. The lazytong linkage 26 extends horizontally between the frame members and itsplane is vertical. The individual links 34 are pivotally connected toeach other at their ends and centers in standard fashion and the upperfree ends are pivotally connected to the upper ends of frame members 22at 36. The lower free ends are also pivotally connected to frame members22 near their lower ends, but in this case the pivot pins 38 ride invertical slots 40 to provide for the necessary motion of the totallinkage; all in known manner. With this construction it will be seenthat each side of the section can be expanded or contracted in unison tochange the length of the section and independently to produce a lateralcurve as shown in FIG. 2.

For reasons to be explained later, it is desirable to provide means toyieldingly expand each section while allowing either partly in section,showing the side of the section to contract independently. For thispurpose a pair of force units 42 are provided for each section. They liesubstantially along the longitudinal centerline with one unit connectedto the upper crossmember 32 and one connected to the lower crossmember32. Each force unit generally comprises a tube 44 and a rod 46telescoping therein, and a coil spring 48 surrounding both members andarranged to urge them apart to expand the force unit. The generalarrangement of the force units is illustrated in FIGS. 3 and 4 and thedetailed construction and connection is illustrated in FIGS. 5 and 8.

Each crossmember 32 is provided at its central lower side with a boxbracket having sideplates 50 and cross plates 52 and 54, the crossplates having vertically aligned apertures 56 to receive a headed pivotpin 58 provided with a cotter pin 60 at its upper end to retain it inposition. In FIG. 8 it will be seen that tube 44 is provided with a cap62 having an aperture car 64 which is mounted on pivot pin 58, the capserving as astop for one end of spring 48. Rod 46 is likewise providedwith a cap 66 having an apertured ear 68 mounted on pivot pin 58 of thenext crossmember. Rod 46 is also provided with a flange 70 which servesas a stop for the opposite end of spring 48. Since the spring is mountedunder compression, it serves to yieldingly expand the force unit andhence the entire section. Because of its pivotal connections, it ispossible to contract one side of the section, compressing the force unitslightly, while the other side remains expanded and the section assumesa laterally curved planform. Each box member serves as the end of onesection and the beginning of another, and there are a pair of forceunits between each two box members as indicated in FIG. 4.

FIGS. 6 and 7 illustrate the pivotal connections between the links 34and the main frame members 22. In FIG. 6, pins 72 pass through the linksand the main frame member and are provided with spacers 74 and withgrommets 76 which slide vertically in slots 40. The pins have a loosefit in the grommets so that the links may swing a few degree laterallyto provide for the curvature of the framework. In FIG. 7, the pins 72pass through the ends and the centers of links 34 and are also providedwith spacers 74 as well as a washer 78 in the center connection.

At the upper pivotal connection of each set of links 34, the flange 80of a crossbar 82 is located between the spacers 74, the crossbarextending across the width of the framework and being provided with asimilar flange and connection at the opposite side. A similar crossbar84 with an upwardly directed flange 86 is connected in the lower pivotalconnection of each set of links. In order to provide track means forsliding travel of a conveyor belt, each crossbar 82 is provided neareach end with a track portion 88 having an upstanding guide flange 90. Aflat wear strip 92 is mounted on the track portion and a channel-shapedwear strip 94 is mounted on the guide flange. Each crossbar 84 isprovided with substantially identical track portions. The upper trackportions combine to form track means for the load-carrying passage ofthe belt and the lower track portions combine to form track means forthe return passage of the belt.

The upper crossmember 32 of each box member is similarly provided with atrack portion 88 to complete the track means, as shown in FIG. 9. All ofthe track portions lie in the same plane to avoid interference withmovement of the belt 28. It will be further noted in FIG. 9 that eachend of portion 88 is cut at a long angle. Referring back to FIG. 2 itwill be seen that this results in angular gaps in the track assemblywhich can expand and contract without forming a gap at right angles tothe line of travel. Thus there is continuous track support for the beltat all times.

As the lazy tong linkage expands and contracts, the lower pivotalconnections of the sets of links 34 rise and fall, as do the crossbarsand track portions. Consequently, no track portions can be mounted onthe lower crossmembers 32 which remain at a fixed height. Instead, anadditional crossbar 84 is provided in the general plane of each boxmember and its flange 86 is mounted on the pivot pin 72 which slides inslot 40, as seen in FIG. 5. A track portion 88 is mounted at each end ofthis additional crossbar 84 to complete the lower track assembly.

The conveyor belt shown in FIG. 2 and in greater detail in FIG.comprises a plurality of small rods 96 extending across the width of thebelt. At each end of each rod is mounted a U-shaped link 98 having ayoke 100 and legs 102. The rod passes through circular apertures 104 inthe end of each leg and is headed over at 106 to maintain the assembly.In addition, each leg is provided adjacent the yoke with an elongateaperture 108. The links are nested as shown so that each rod passesthrough apertures 104 of its own link and apertures 108 of the nestedlink. Thus the belt is flexible about the axis of each rod and mayexpand and contract to the extent of travel of each rod in the nestedlink. On a lateral curve, as in FIG. 2, thebelt is fully expanded at theoutside of the curve sufficiently to produce the amount of curvaturedesired for the particular installation. The links slide along the trackportions previously described, and guide flanges 90 prevent lateralmovement of the belt inwardly of its proper path around a curve.

When it is necessary or desirable to cover the open spaces between therods, a series of individual cover plates 110 are provided. As seen incross section in FIG. 11, each plate is generally T-shaped, having anupper crossmember 112 and a pair of depending legs 114, 116. The plateis preferably a plastic extrusion, and the material is resilient enoughto snap the legs over a rod 96 into the elongate recess between thelegs. In the event of damage or excessive wear, they are readily removedand replaced.

A modified form of link is shown in FIG. 12, and comprises a die-cast ormolded plastic block 118 having angular ends to provide an overlappingassembly. Rod 96 passes through a circular opening 120 in its own linkand through an elongate opening 122 in the next link and is headed overat 106. The action is the same as in the form of FIG. 10 but he linkshave a much larger rubbing surface which reduces wear on both the linksand the wear strips of the track portions.

A protective curtain or shield is shown in FIG. 7 and includes a seriesof short strips 124 of preferably plastic material mounted in horizontalposition by brackets 126 to the crossmembers 32 and crossbars 82 tooverlie links 98, and having depending flanges 128. Each strip isprovided with an underlying wear strip 130 slightly spaced above thelinks and serving to prevent them from leaving the track portions.Strips 124 also protect the hands of operators from contact with thelinks. Depending from flanges 128 is an accordion-type curtain 132 toshield the side portion of the framework. The accordion formation allowsthe curtain to expand and contract with the framework.

Since the force units are connected in series from end to end, it willbe apparent that when the apparatus is in straight line attitude theframework will expand until the belt is fully expanded and springtensioned. Slots 40 in frame members 22 are long enough so that theframework may both expand and contract to a greater extent than the beltand thus permit the belt to attain its maximum curvature when desired.In order to provide lateral bending flexibility along all portions ofthe framework both at and between the main frame members, all pivotalconnections are provided with sufficient play to permit the necessaryangular movement.

Standards 24 comprise upper tubular struts 134 and lower caster rods 136carrying wheels 138 to facilitate movement in all directions forplacement of the apparatus. This arrangement also makes it possible tochange the orientation of the apparatus while it is in operation. Thisis particularly valuable when the receiving operator must move fromplace to place, as along a warehouse wall, in order to reach additionalstorage area. Latch means 140 serves to lock the casters againstrotation when the apparatus is in a desired conformation.

It will be apparent to those skilled in the art that various changes maybe made in the construction and arrangement of parts as disclosedwithout departing from the spirit of the invention and it is intendedthat all such changes shall be embraced within the scope of thefollowing claims.

We claim:

1. The combination of an endless loop flexible conveyor belt and acarrier support therefor; said belt comprising a plurality of lostmotion linkages connected to provide longitudinal expansion andcontraction of the side edges of said belt jointly or separately topermit lateral curvature in the plane of the belt; said supportcomprising an articulated structure having an elongate generallyrectangular planform and provided with means to maintain its upperportion at a desired height above ground level; said upper portion beingprovided with track means at each side to support the side edges of saidbelt for sliding movement therealong; transfer means at each end of saidcarrier support to engage said belt and guide it in a return direction;the articulated structure providing means for independent longitudinalexpansion and contraction of each side of said support to approximatelythe same extent as the longitudinal expansion of said belt; and eitherside of said support being contractable in unison with the correspondingside edge of the belt to curve the combination apparatus laterally in agenerally horizontal plane while leaving the opposite side fullyexpanded to maintain tension in the belt.

2. The combination as claimed in claim 1; and force-applying means toapply yieldable longitudinal expanding force to said support and producea desired degree of tension in said belt; the contraction of one side ofthe support and belt serving to overcome the force-applying meanssufficiently to produce the desired degree of curvature withoutpreventing the force applying means from maintaining expansion of theother side of the support and belt.

3. The combination as claimed in claim 1; said support being expandableand contractable through a greater range than said belt to ensure fullexpansion and tensioning of the belt and maximum contraction of theselected side edge of the belt for minimum turn radius.

4. The combination as claimed in claim 1; said track means serving tosupport the load-carrying portion of said belt; and second track meansspaced below the first said track means at each side of the support andserving to support the return portion of said belt.

5. The combination as claimed in claim 1; the track means at each sideof said support comprising a series of longitudinally spaced discretetrack portions uniformly movable toward and away from each otherlongitudinally as the support contracts and expands.

6. Flexible conveyor apparatus for supporting an endless loop flexibleconveyor belt which is adapted to expand and contract longitudinally ateach side edge jointly or independently to produce lateral curvature inthe plane of the belt, comprising: An elongate framework having agenerally rectangular planform and having at least two longitudinallyspaced upright main frame members at each side: means to maintain themain frame members at a desired height above ground level; at least onecrossmember rigidly connecting each set of two laterally opposed mainframe members to maintain them in predetermined relation to each other;longitudinally expandable and contractable connector means extendingbetween each pair of longitudinally successive main frame members ateither side of said framework to provide for longitudinal separation andapproach of the frame members at one side of the framework independentlyof the frame members at the opposite side; contraction of the connectormeans at one selected side while the opposite connector means remainsexpanded serving to produce curvature of the framework in a horizontalplane; longitudinally extending track means carried by the frameworkalong each side to support the belt in sliding relation; and transfermeans at each end of the framework to engage the belt and guide it in areturn direction; the track means at each side of said frameworkcomprising a series oflongitudinally spaced discrete track portionsuniformly movable toward and away from each other longitudinally as theframework contracts and expands.

7 Apparatus as claimed in claim 6; and force-applying means to applyyieldable longitudinal expanding force to said framework; said forcebeing selectively yieldable to longitudinal contraction of either sideof said framework independently of the opposite side.

8 Apparatus as claimed in claim 7; said force-applying means comprisinga force unit extending between each successive pair of crossmembers; theforce unit including a telescoping rod and tube having free endsconnected to the successive crossmembers and a coil spring arranged tourge the rod out of the tube to increase the overall length of the forceunit.

9. Apparatus as claimed in claim 8; said framework including acrossmember extending between the upper ends of each set of twolaterally opposed main frame members and a secondcrossmember extendingbetween the lower ends of said main frame members, all being rigidlysecured to form a rigid boxlike structure; one force unit extendingbetween each two successive upper crossmembers and one force unitextending between each two successive lower crossmembers; said forceunits lying substantially on the longitudinal centerline of theframework and being pivotally connected to the crossmembers.

10. Apparatus as claimed in claim 6; the connector means between twomain frame members at either side of the framework comprising anarticulated lazy-tong-type parallelogram linkage extending generallyhorizontally and with the plane of the linkage generally vertical; thefree ends of the linkage being pivotally connected to the main framemembers to constitute a trusslike arrangement.

11. Apparatus as claimed in claim 10; the track means at each side ofsaid framework comprising a series of longitudinally spaced discretetrack portions; one track portion being carried by the upper end of eachmain frame member and one track portion being carried by the upper apexpivotal connection of each set of lazy tong links; all of said trackportions lying in a common horizontal plane.

12. Apparatus as claimed in claim 11; and a second set of discrete trackportions at each side of said-framework spaced directly below the firstset and similarly connected to the lower apex pivotal connection of eachset of lazy tong links and to the lower pivotal connection of one endlink to each main frame member.

13. Apparatus as claimed in claim 10; the pivotal connections of thelazy tong links with each other and with the main frame members beingprovided with a small amount of play to provide for angular variation ina horizontal plane between each set of links and the frame membersresulting in horizontal curvature of the framework.

14. Apparatus as claimed in claim 8; in which one track portion iscarried by each main frame member and a plurality of track portions arearranged in spaced relation between two main frame members and carriedby the connector means.

15. Apparatus as claimed in claim 6; the means to maintain the mainframe members at a desired height comprising standards extendingdownwardly from the main frame members; and castered wheels at the lowerends of said standards to facilitate repositioning of parts of theframework while the apparatus is in operation.

16. apparatus as claimed in claim 16; and means to lockthe wheelsagainst castering to prevent displacement of v the framework duringoperation. I

1. The combination of an endless loop flexible conveyor belt and acarrier support therefor; said belt comprising a plurality of lostmotion linkages connected to provide longitudinal expansion andcontraction of the side edges of said belt jointly or separately topermit lateral curvature in the plane of the belt; said supportcomprising an articulated structure having an elongate generallyrectangular planform and provided with means to maintain its upperportion at a desired height above ground level; said upper portion beingprovided with track means at each side to support the side edges of saidbelt for sliding movement therealong; transfer means at each end of saidcarrier support to engage said belt and guide it in a return direction;the articulated structure providing means for independent longitudinalexpansion and contraction of each side of said support to approximatelythe same extent as the longitudinal expansion of said belt; and eitherside of said support being contractable in unison with the correspondingside edge of the belt to curve the combination apparatus laterally in agenerally horizontal plane while leaving the opposite side fullyexpanded to maintain tension in the belt.
 2. The combination as claimedin claim 1; and force-applying means to apply yieldable longitudinalexpanding force to said support and produce a desired degree of tensionin said belt; the contraction of one side of the support and beltserving to overcome the force-applying means sufficiently to produce thedesired degree of curvature without preventing the force applying meansfrom maintaining expansion of the other side of the support and belt. 3.The combination as claimed in claim 1; said support being expAndable andcontractable through a greater range than said belt to ensure fullexpansion and tensioning of the belt and maximum contraction of theselected side edge of the belt for minimum turn radius.
 4. Thecombination as claimed in claim 1; said track means serving to supportthe load-carrying portion of said belt; and second track means spacedbelow the first said track means at each side of the support and servingto support the return portion of said belt.
 5. The combination asclaimed in claim 1; the track means at each side of said supportcomprising a series of longitudinally spaced discrete track portionsuniformly movable toward and away from each other longitudinally as thesupport contracts and expands.
 6. Flexible conveyor apparatus forsupporting an endless loop flexible conveyor belt which is adapted toexpand and contract longitudinally at each side edge jointly orindependently to produce lateral curvature in the plane of the belt,comprising: An elongate framework having a generally rectangularplanform and having at least two longitudinally spaced upright mainframe members at each side: means to maintain the main frame members ata desired height above ground level; at least one crossmember rigidlyconnecting each set of two laterally opposed main frame members tomaintain them in predetermined relation to each other; longitudinallyexpandable and contractable connector means extending between each pairof longitudinally successive main frame members at either side of saidframework to provide for longitudinal separation and approach of theframe members at one side of the framework independently of the framemembers at the opposite side; contraction of the connector means at oneselected side while the opposite connector means remains expandedserving to produce curvature of the framework in a horizontal plane;longitudinally extending track means carried by the framework along eachside to support the belt in sliding relation; and transfer means at eachend of the framework to engage the belt and guide it in a returndirection; the track means at each side of said framework comprising aseries of longitudinally spaced discrete track portions uniformlymovable toward and away from each other longitudinally as the frameworkcontracts and expands.
 7. Apparatus as claimed in claim 6; andforce-applying means to apply yieldable longitudinal expanding force tosaid framework; said force being selectively yieldable to longitudinalcontraction of either side of said framework independently of theopposite side.
 8. Apparatus as claimed in claim 7; said force-applyingmeans comprising a force unit extending between each successive pair ofcrossmembers; the force unit including a telescoping rod and tube havingfree ends connected to the successive crossmembers and a coil springarranged to urge the rod out of the tube to increase the overall lengthof the force unit.
 9. Apparatus as claimed in claim 8; said frameworkincluding a crossmember extending between the upper ends of each set oftwo laterally opposed main frame members and a second crossmemberextending between the lower ends of said main frame members, all beingrigidly secured to form a rigid boxlike structure; one force unitextending between each two successive upper crossmembers and one forceunit extending between each two successive lower crossmembers; saidforce units lying substantially on the longitudinal centerline of theframework and being pivotally connected to the crossmembers. 10.Apparatus as claimed in claim 6; the connector means between two mainframe members at either side of the framework comprising an articulatedlazy-tong-type parallelogram linkage extending generally horizontallyand with the plane of the linkage generally vertical; the free ends ofthe linkage being pivotally connected to the main frame members toconstitute a trusslike arrangement.
 11. Apparatus as claimed in claim10; the track means at each side of said framework comprising A seriesof longitudinally spaced discrete track portions; one track portionbeing carried by the upper end of each main frame member and one trackportion being carried by the upper apex pivotal connection of each setof lazy tong links; all of said track portions lying in a commonhorizontal plane.
 12. Apparatus as claimed in claim 11; and a second setof discrete track portions at each side of said framework spaceddirectly below the first set and similarly connected to the lower apexpivotal connection of each set of lazy tong links and to the lowerpivotal connection of one end link to each main frame member. 13.Apparatus as claimed in claim 10; the pivotal connections of the lazytong links with each other and with the main frame members beingprovided with a small amount of play to provide for angular variation ina horizontal plane between each set of links and the frame membersresulting in horizontal curvature of the framework.
 14. Apparatus asclaimed in claim 8; in which one track portion is carried by each mainframe member and a plurality of track portions are arranged in spacedrelation between two main frame members and carried by the connectormeans.
 15. Apparatus as claimed in claim 6; the means to maintain themain frame members at a desired height comprising standards extendingdownwardly from the main frame members; and castered wheels at the lowerends of said standards to facilitate repositioning of parts of theframework while the apparatus is in operation.
 16. apparatus as claimedin claim 16; and means to lock the wheels against castering to preventdisplacement of the framework during operation.